Last year, the American Library Association (ALA) and others, challenged CIPA, claiming such filters are a form of censorship. The ALA won in a lower court, but the Supreme Court ruled 6 to 3 on Monday to uphold CIPA.

"Most libraries already exclude pornography from their print collections because they deem it inappropriate for inclusion. We do not subject these decisions to heightened scrutiny; it would make little sense to treat libraries' judgments to block online pornography any differently...." wrote Chief Justice Rehnquist for the court.

While the entire court rightly acknowledged the severity of online smut, and took an appropriately hard line against Web porn, the majority of justices failed to acknowledge that many libraries already have their own sensible Internet-use policies, such as parental monitoring, privacy screens, and separate spaces for adults and children using computers. Libraries, though, do have some leeway in implementing the law.

The ALA also claimed that filters "overblock" legitimate websites. But the court said that was "... dispelled by the ease with which patrons may have the filtering software disabled."

The court may find itself wrestling in a future case over a different free speech-related issue: Just how much power should government give the makers of filtering software? At the same time, a need for better filtering technology that does not screen out legitimate websites remains.

For now, the ruling should help protect kids from porn and still ensure the free flow of useful information at public libraries.